1. Field of the Invention
This invention relates generally to a synchronization pulse separator circuit and, more particularly, to a digital synchronization pulse separator circuit for use with a variety of video signal formats.
2. Description of the Prior Art
Video signals are generally unique in the sense that they contain color, brightness and synchronization information all within the same signal in the form of phase, amplitude and pulse width modulation respectively. All the brightness information is generally contained in the positive amplitude of the signal above a predetermined voltage while the horizontal and vertical synchronization signals contained pulses which fall below the predetermined voltage level. Such video signals may be in the well-known RS - 170 type format generally used for commercial broadcasting or alternatively may be in a variety of other formats such as those generated by home and personal computers like DiAnza, Apple, and IBM small computers which do not adhere to the broadcasting industry's format. Video signals are generally processed by first stripping off the brightness information contained in the voltage amplitudes above the predetermined level thereby leaving a composite pulse synchronization signal comprising both horizontal synchronization pulses and vertical synchronization pulses which are then separated from the composite pulse synchronization signal by what are conventionally known as synchronization pulse separator circuits. Such pulse separator circuits are generally designed to accommodate a video signal having a particular format and frequency by selecting particular components involving RC time constant determining elements.
However, not only may the format of the video signal vary as previously discussed, but also the resolution of the line scan may vary particularly for high resolution systems in which the line scan rates may be many times higher than that of basic RS - 170 broadcasting. In addition, even for low resolution systems in which scan rates are relatively lower, various frequencies can be found. For example, in the United States, horizontal frequencies are derived from a 60 hertz field rate, whereas in Europe such frequencies are derived from 50 hertz field rates. Thus, such pulse separator circuits are usually designed to be dedicated to decode only one composite pulse synchronization signal having a specific format and frequency.
Therefore, it is a primary object of this invention to provide a synchronization pulse separator circuit that is automatically compatible for use with various formats and frequencies of video signals.
It is a further object of this invention to provide a synchronization pulse separator circuit for use with video signals of various formats and frequencies without the need for the user to change or adjust either components or other parameters responsive to component adjustments.
It is an even further object of this invention to provide a digital pulse synchronization separator circuit which automatically operates to decode video signals having a variety of different formats and frequencies.
Other objects of the invention will be in part obvious and will in part appear hereinafter. The invention accordingly comprises a mechanism and system possessing the construction, combination of elements and arrangement of parts which are exemplified in the following detailed disclosure.